A loader permitting a boat to be conveniently lifted from an upright position alongside a vehicle to an inverted position atop the vehicle includes a pair of tracks extending transversely across the top of the vehicle and downwardly along the side of the vehicle, and a carriage mounted for travel along the tracks between a raised transport position and a lowered loading and unloading position. A cable is connected with a winch and extends around a pair of sheaves located on opposite sides of the carriage to extend from the winch to a lower or far side sheave, then to an upper or near side sheave, and then to the boat. In loading a boat, retracting the cable first tilts the boat sideways into contact with the carriage and then raises both the carriage and the boat to the transport position. The apparatus permits a boat to be loaded onto or unloaded from the top of a vehicle used to tow another vehicle such as a camping trailer without the need to first unhitch the trailer.